Coordinated afterburner fuel control and exhaust nozzle area control for gas turbine engine



Dm., '59 w66 F. Pz. ROGERS WAL JSQM COORDINATED AFTERBURNEB FUEL CONTROLAND EXHAUST NOZZLE AREA CONTROL FOR GAS TURBINE ENGINE 13, 1963Sheets--Sheet l Original Filed Sept.

/ymew mc n AQQENT n w Y, Das@ @9 M COORDINATED AFTERBURNER FUEL CONTROLAND EXI'MUST NOZZLE AREA CONTROL FOR GAS TURBXNE lNGNE Original FiledSept. 3.15, 19615 F ElslxawSheGt 2 l il /97 44/ H613 ww w [N VEN T0125Dm; @2, fefrnfcasim f COORDINATED AFTERBURNLR FUEL CONTRQL ma EXHAUSTAREA CONTROL FOR GAS www5: :mmm: Original Filed Sept. l5, 1965 7'Slzuaes'izswneet 3 www IN VENTORS AREA CONTROL FOR GAS TURBINE ENGlLIEOriginal Filed Sepi. 3.31, 1963 INVENTOR @ma MM@ GOORDINATED AFTERBURNERFUEL AREA CDNTBOL FOR GAS TURBINE ENGIN Original Filed Sepia 13,

Dem., 6 E96@ F. n. RGGEW@ H1-ML @,QW

COORDINATED AFTERBURNER FUEL CONTROL AND EXHAUST NOZZLE AREA CONTROL FORGAS TURBINE ENGINE Original Filed Sept. l5, 1965 7 Sheets-Sheet 6 Wm@SE1 EET ML.

7 Sheezs GOORDINATED AFTERBURNER FUEL CONTROL AND EXHAUST AREA CONTROLFOR GAS TURBINE ENGINE 7 :mass

N VENTURI? WC1? E N 7' Original Filed Sept United States Patent OCOORDINATED AFTERBURNER FUEL CONTROL AND EXHAUST NOZZLE AREA CONTROL FORGAS TURBINE ENGINE Francis R. Rogers, Howard L. McCombs, Jr., and MikeSnider, South Bend, Ind., assignors to The Bendix Corporation, acorporation of Delaware Original application Sept. 13, 1963, Ser. No.308,799, now Patent No. 3,232,053, dated Feb. 1, 1966. Divided and thisapplication Oct. 22, 1965, Ser. No. 501,443

Claims. (Cl. 60-237) This is a division of application Serial No.308,799, filed September 13, 1963 now U.S. Patent No. 3,232,053, issuedFebruary 1, 1966.

This invention relates in general to control apparatus for ra combustionengine and, in particular, to fuel control apparatus for a gas turbineengine having a variable area exhaust nozzle.

It is an object of the present invention to provide a fuel control forreliably and accurately controlling the flow of fuel to a combustionengine as a function of predetermined engine operating conditions.

It is another object of the present invention to provide an easilyserviced lightweight fuel control for an aircraft combustion engine.

It is still another object of the present invention to provide fuel feedand power control apparatus having a main fuel control, an afterburnerfuel control and a nozzle area control operative together in responselto a plurality of variable engine operating conditions to maintain fuelfeed and exhaust nozzle area within prescribed limits over the entireoperating range of the engine as a function of the variable engineoperating conditions.

It is an important object of the present invention to provide a fuelcontrol having a mechanical computer section and a fuel metering sectionfor an aircraft gas turbine engine which fuel metering section operateson the basis of ia constant pressure head across a variable meteringValve area and which computer section operates to receive a plurality ofinput signals representative of variable engine operating conditionssuch as engine throttle lever request, engine speed, compressordischarge pressure and compressor inlet `air pressure and temperatureand mechanically computed control signals therefrom to thereby establisha metering valve area which is a function of one or more of saidvariable engine operating conditions.

It is yet another object of the present invention to provide 4fuel feedvand power control apparatus for an aircraft gas turbine engine whichmay be easily modified for operation with different engines of the sametype but with varying operating characteristics which must becompensated for by the fuel feed and power control apparatus.

Other objects and advantages of the present invention will becomeapparent from the following description taken in conjunction with theaccompanying drawings wherein:

FIGURE 1 is a schematic representation of an aircraft jet engineembodying the present invention wherein the component sections of thepresent invention are shown in block form;

FIGURE 2 is a schematic representation showing structural details of aportion of the main fuel control shown in block form in FIGURE 1;

FIGURE 3 is a schematic representat-ion showing structural `details ofthe remaining portion of the main fuel lcontrol shown in block form inFIGURE l;

FIGURE 4 is a schematic representation showing structural details of aportion of the afterburner fuel control shown in block form in FIGURE l;

3,289,411 Patented Dec. 6, 1966 ICC FIGURE 4a is a schematicrepresentation showing structural details of the remaining portion ofthe rafterburner fuel control shown -in block form in FIGURE l;

FIGURE 5 is `a schematic representation showing structural details of aportion of the exhaust nozzle area control shown in block form in FIGURE1; and

FIGURE 6 is a schematic representation showing structural details of theremaining portion .of the exhaust nozzle :area control shown in blockform in FIGURE 1.

Referring to FIGURE l, numeral 20 represents an 1aircraft gas turbineengine of the turbo-fan type which is provided with inner and outercasings 21 and 22, respectively, which form an annular air duct 23leading from air inlet 24 to yan afterburner section 25 of casing 22which terminates in a variable area exhaust nozzle 26 having movableexhaust nozzle gates 27. A fan 28 and low pressure air compressor'29 aresecured to and driven by a dual turbine 30 via a shaft 31 rotatablycarried in bearings, not shown. A high pressure air compressor 32 inseries with compressor 29 is secured to and driven by a turbine 33 via ashaft 34 concentric with shaft 31 and rotatably carried by bearings, notshown, for independent rotation relative to shaft 31. A plurality ofcombustion chambers 35 is supplied fuel by fuel nozzles 36 connected toannular fuel manifold 37. A plurality of annular a-fterburner fuelmanifolds 38, 39 and 40 are arranged to inject fuel into duct 23 and/orcasing 22 upstream from flame holders 41 which are secured to casing 22.

Air flows into inlet 24 and is compress-ed and displaced rearwardly intoduct 23 as well as low pressure air compressor 29 by fan 28, thecompressor 29 pressurizing its associated air flow and delivering thesame to the high pressure air compressor 32 which, in turn, furtherpressurizes the air and discharges to combustion charnbers 35 whereinthe mixture .of fuel and air is burned to form a hot motive gas whichows through turbines 33 and 30 driving the same. The hot motive gas isdischarged from turbine 30 and together with air exhausted from duct 23flows through exhaust nozzle 26 and expands to the atmosphere therebyproviding a propelling thrust. Fuel nozzles 42 connected to afterburnerfuel manifolds 38, 39 and 40 are arranged to inject fuel into the gasdownstream of the turbine 33 where the injected fuel is burned toelevate the temperature of the gas thereby providing a correspondingincrease in thrust.

Metered fuel flow is supplied to the fuel manifold 37 from a main fuelcontrol 43 via a fuel conduit 44 connected therebetween. The main `fuelcontrol 43 is supplied pressurized fuel via a fuel supply conduit 45leading to a fuel tank 46 and containing an engine driven positivedisplacement fuel pump 47. A conventional gear and shafting arrangement48 provides a driving connection between the pump 47 and engine shaft31. Various control input signals associated with engine operation aresupplied to the main fuel control 43 which establishes metered fuel flowto conduit 44 as a function of the various input signals and whichtransmits computed pressure signals to other component sections of thesystem as will be described hereinafter. Among the control input signalsare compressor inlet air pressure P, and temperature T, which aretransmitted to the main fuel control 43 via conduit 49 and temperaturepick-up unit 50, respectively, suitably disposed in air inlet 24. Therotational speed N2 of the high pressure air compressor 32 istransmitted to the main fuel control 43 via conventional gearing andshafting arrangement generally indicated by numeral 51. High pressurecompressor discharge air pressure Pc is transmitted to the main fuelcontrol via conduit 52. A ydrain passage 53 communicates the interior ofthe main fuel control 4-3 with fuel conduit 45 at fuel pump inlet ordrain pressure P0. A

Q manually operative throttle lever 54 movable between cut-off and amaximum afterburner position provides a power request signal to the mainfuel control 43.

Metered fuel flow is supplied to Ithe aftenburner fuel manifolds 38, 39and `40 from yan afterburner fuel control `55 via fuel conduits 56, 57and 58, respectively, connected therebetween. The iafterburner fuelcontrol 55 is supplied pressurized fuel via a fuel supply conduit 59leading to fuel tank 46 and containing an engine driven centrifugal fuelpump 60. Among the control input signals supplied to the afterburnerfuel control 55 are compressor inlet temperature T1 and compressordischarge air pressure Pc which are supplied via tempenature sensingunit 61 and conduit 62, respectively. A drain passage 63 communicatesthe interior of afterburner fuel control 55 with conduit 53 at fuel pumpinlet pressure P0.

The position of the variable area gates 27 is controlled by `a powerunit which includes 1a cylinder 64 and a piston 65 slidable therein.Fluid pressure is supplied to opposite sides of the piston 65 viapassages 66 and 68 leading to an exhaust nozzle control 70 whichcontrols the fiow of fiuid therethrough as a function of various inputcontrol signals. The input control signals include the position ofthrottle lever `54 received via shaft 71 and air pressures PT4 and PTqupstream and downstream of turbines 33 and 30, respectively, viapassages 72 and 73, respectively. The position of gates 27 istransmitted to nozzle control 70 via mechanical feedback mechanismincluding a spning loaded pulley 74 and flexible link 75 connectingpulley 74 and piston 65. A conduit 76 containing an engine driven fuelpump 76 communicates pressurized fuel to exhaust nozzle con-trol 70 fromfuel source 46.

Referring to FIGURES 2 and 3 which together illus- Itrate the variouscomponent portions of the main fuel control 43, numeral 77 :designates acasing through which fuel flows from supply conduit 45 to fuel conduitv44 via a flow conduit 78 containing fuel filters 79 and 80, a variable:area orifice 81, a fuel pressure responsive spring loaded valve 82 anda spring loaded check valve 83. A metering valve 84 operativelyconnected to orifice 81 is provided with opposite end portions 85 and 86slidably carried in casing 77 and, iat one end, is provided with anintegral servo piston 87 slidably carried in casing 77 and togetherwit-h casing 77 defining variable volume chambers 88 and 89. Fuel at lapredetermined constant regulated fuel pressure Pr is supplied to chamber88 via a conduit 90 connected to flow conduit 78 and provided with aconventional spring loaded pressure responsive pressure regulating valve91 which, depending upon the spring load applied thereto, regulates thepressure o-f the fuel downstream therefrom at a predetermined constantvalue Pr. Fuel fiows from chamber 88 to chamsber 89 via -a fixed arearestriction 92 fixedly secured in piston 87 and then flows to theinterior of casing 77 at drain pressure P.o via a passage 93. The flowthrough passage 93 and thus the pressure drop across piston `87 iscontrolled by a variable area orifice 94 which is operatively connectedto the discharge end of passage 93. It will be noted that the pis-tonI87 has a relatively large area exposed to the lower fuel pressure inchamber 89 derived from pressure Pr such that piston 87 is stabilizedwhen the inverse ratio of fuel pressures thereacross equals the arearatio of piston `87 and is moving when said ratio of pressures is upset.An adjustable maximum flow stop 95 threadedly engaged with casing 77 isadapted to engage piston 87 thereby limiting movement of metering valvel84 in .an opening direction. An adjustable minimum fiow stop whichincludes a threaded member 96 threadedly engaged with casing '77 and alever member 97 pivotally secured to casing 77 'and member 96 is adaptedto engage end portion 86 thereby limiting movement of metering valve `84in a closing direction.

The position of metering valve 84 and thus fuel flow through conduit 44to the engine is regulated as a function of .the speed N2 of highpressure -air compressor 32 by a governor and `acceleration cam havingseparate circumferential portions 98 and 99 which are contoured radiallyas predetermined functions of high pressure air compressor speed N2 toprovide corresponding governing :and acceleration fuel flows,respectively. The cam portion 99 is countoured axially as a function ofcompressor inlet air temperature Ti to provide temperature compensationfor acceleration fuel flow.

A .second cam fixedly secured to cam portions 98 and 99 is provided withseparate circumferential portions 100 and 101 which 'are contouredradially as predetermined function of -high pressure air compressor`speed N2.

The governor and acceleration cam and second cam secured thereto areslidably mounted for axial movement on a shaft 102 and -are rotatablewith shaft 102 which is journalled at one end in casing 77 and which isprorvided with an integral pinion 103 at the opposite end. The pinion103 is engaged by a rack 104 iixedly secured to a servo piston 105 whichserves to rotate pinion 103 and shaft 102 as a function of high pressurecompressor speed N2 in response to movement of piston 105. A camfollower 106 is urged into engagement with portion 99 of the governorand acceleration cam by a lever 107 pivotally connected at one end tothe cam follower 106 and at the opposite end pivotally connected to areduced diameter extension 108 of a servo piston 109. A spring 110suitably interposed between lever 107 and casing 77 serves to bias thelever 107 to effect engagement of follower 106 with cam portion 99 whenthe lever 107 is biased out of engagement with an adjustable fulcrum orabutment member 111 by servo piston 109 as shown in FIGURE 2. Thefulcrum or abutment member 111 is adjustably secured to casing 77 by ascrew 112 threadedly engaged therewith. A cam follower 113 is urged intoengagement with cam portion 98 by a lever 114 pivotally connected -atone end to follower 113. A tension spring 115 connected to casing 77 andlever 114 serves to load lever 114 `in a counterclockwise direction. Theopposite end of lever 114 is adapted to engage a ball servo valve 116which cooperates with -a valve seat 117 formed at the discharge end of apassage 118 defined by an annular extension 119 integral with servopist-on 109 which annular extension extends through an opening 120 incasing 77. An `adjustable fixed stop 121 threadedly engaged with casing77 is engageable with lever 114 to thereby limit movement of the same.The reduced diameter section 108 extends from the opposite side of servopiston 109 through an opening 1.22 in casing 77. The servo piston 109 isslidably carried in `a charnber 123 and arranged to engage `a stop 124which engagement permits the lever 107 to occupy a slight spacedrelationship relative to adjustable fulcrum 111 when the follower 106occupies a position corresponding to the maximum depression of contouredportion 99. Fuel at constant regulated servo pressure Pr is supplied tochamber 123 via a passage 125 leading from conduit 90 and flows througha restriction 126 fixedly secured in piston 109 to chamber 123 on theoppos-ite side of piston 109 from which it flows through passage 118 tothe interior of casing 77 at drain pressure P0. The fuel pressure Ps inchamber 123 on the downstream side of restriction 126 is controlled bythe ball valve 116. The larger and smaller effective areas of piston 109exposed to fuel pressures Ps and Pr, respectively, have a predeterminedfixed area ratio which requires that a corresponding ratio of pressuresPS and Pr be established to stabilize piston 109 at any position in itsrange of travel. The piston 109 will respond -to a variation from thepredetermined pressure ratio Pr/Ps and continue to move until the -fuelpressure Psis regulated by the action of ball valve 116 to the valuerequired to es-tablish the predetermined ratio Pr/PS. It will be notedthat the servo piston 109 is of the follow-up type which means that,depend-ing upon the direction of movement of ball valve 116 relative tovalve seat 117, the piston 109 will move .in the same direction inresponse to the change in pressure Ps until the position of valve seat117 relative to ball valve 116 is such that the pressure Is required tostabilize piston 109 is again re-established. For -additional details ofthe governor and acceleration cam and associated linkage mechanismdescribed above, reference is made to U.S. Patent No. 3,138,926 issuedJune 30, 1964, in the name of H. L. McCombs, Jr. (common assignee). Theposition of the ball valve 116 for a fixed position of follower 113 isdependent upon the position of a spring loaded follower 127 lattached tolever 114 through a rod 1218, a bell crank 129 pivotally secured at onearm to rod 128 and pivotally secured -to casing 77 at its midsection, afollower 130 slidably engaged with the other arm of bell crank 129 andpivotally connected to a rod 131 which, in turn, is pivotally connectedto lever 1114. The follower 127 is responsive to the position of a speedrequest cam 132 slidably mounted on a shaft 133 Iand rotatable therewithin response to movement of throttle lever 54. Throttle lever 54 isfixedly secured to a gear 134 `which meshes with Va gear 135 fxedlysecured to the shaft 133. An engine idle speed adjustment includes anadjustable fixed :stop 136 pivotally secured to casing 77 and at one endpivotally secured to a rod 137 threadedly engaged with casing 77. Thestop 136 is adapted to engage a flange 138 iixedly secured to rod 131 tothereby limit movement of the same in a corresponding direction. The-movement of rod 131 in the opposite direction is limited by a stopmember 139 which engages a flange 140 fixedly secured to rod 131. Thestop member 139 is pivotally secured to casing 77 and provided with anarm 141 which is biased against an adjustable xed stop 142 threadedlyengaged with casing 77 by a rod 143 integral with a piston 144. Thepiston 144 is slidably carried in a chamber 145 and is biased away fromarm 141 by a spring 146 interposed between casing 77 and piston 144 Ianddrain fuel pressure Po acting against one side of piston 144. The rod143 is biased against arm 141 by constant regulated fuel pressure Prwhich communicates with chamber 145- at the opposite side of piston 144via a passage 1'48 -leading to conduit 90. The passage 148 is vented todrain fuel pressure Po via -a restriction 149. A normally closed valve150 in passage 148 is actuated by an electrical solenoid 151 which isenergized at a predetermined throttle lever 54 position by a switch 152.A cam 153 rotatable with throttle lever 54 serves to activate switch 152at the predetermined throttle lever position. With valve 150 closed, thefuel at pressure PT in chamber 147 is permitted to drain to the interiorof casing 77 at pressure Po via restriction 1'49.

The servo piston 105 which actua-tes rack 104 is slid- Iably carried ina chamber 154 which receives fuel at constant regulated servo pressurePr via passage 125 vented thereto. Fuel flows through a restriction 155iixedly secured in piston 105 to chamber 154 at the opposite side ofpiston 105 from which the fuel flows through a passage 156 having avariable area valve 157 at the discharge end thereof to the interior ofcasing 77 at drain pressure P0. The effective flow area of valve 157 iscontrolled as a function of high pressure compressor speed N2 by a lever158 pivotally secured to casing 77 and engageable at one end with abearing member 159v slidably carried on a rod 160 which, in turn, isintegral with a rotatable support 161. The support 161 is provided witha shaft 162 ha'ving a gear 163 integral thereto which is driven by thehigh pressure compressor 32 via gearing and shafting 51. A pair ofcentrifugal weights 164 pivotally secured to support 161 extends intoengagement with the beaning member 159 to thereby load the same axiallyin response to the centrifugal force derived from the rotation of theweights 164. The force applied to lever 158 by bearing member 159 isopposed by a constant reference force derived from a spring 165 which isapplied to lever 158 Ithrough a plate 166 and roller 167 which contactsplate 166 and -lever 158 land rolls therebetween. The opposite end ofspring 1165 is engaged by a spring retainer 168 provided withtemperature responsive discs 169 secured thereto which are supported bya retaining member 170 fixedly secured to casing 77. The discs 169provide temperature compensation relative to the fuel .surroundingspring 165. The roller 167 is pivotally secured to a yoke 171 which, inturn, is pivotally secured to one end of ya lever 172. The lever 172 ispivotally secured to casing 77 at its intermediate portion and at itsopposite end is pivotally :secured to a follower 173 which bears againstcontoured portion 100. A tension spring 174 connected to casing 77 andlever 17'2 serves to load the lever 172 in a clockwise direction.

The governor and Vacceleration cam )and second cam secured thereto areactuated axially on shaft 102 as a. function of compressor inlet airtemperature T1 by a piston 175 integral with a rack 176 which isprovided with a retaining annulus 177. One end of a lever 178 pivotallysecured to casing 77 is retained by annulus 177 and the opposi-te end oflever 178 is retained by a retaining annulus 179 formed on the secondcam. The piston 175 slides in 4a chamber 180 to which fuel at regulatedservo pressure Pr is supplied via .a passage 181. Fuel flows through arestriction 182I xedly secured in piston 175 to chamber 180 at theopposite side of piston 175 from which the fuel flows to the interior ofcasing 77 at drain pressure Po via a passage 1'83 having a variable`area valve 184 at the discharge end thereof. The effective ow area ofpassage 183 and thus fuel pressure Ps in chamber is varied by valve 184in response to movement of a lever 185 pivotally connected at one end torack 176. The opposite end of lever 185 is engaged by an arm 186pivotally secured to casing 77. The arm 186 is actua-ted by a roller 187which rides against a beveled surface 188 formed on a cylindrical member189 slidably carried by casing 77 and iixedly secured to a movable endof a bellows 190 which is filled with a uid which expands and contractsaxially in response to compressor inlet temperature T sensed by unit 50.The roller 187 is rotatably secured to a yoke 191 which is pivotallysecured to one end of a bell crank 192. The bell crank 192 is pivotallysecured to casing 77 and is pivotally secured at its opposite end to themovable end of a bellows 193 which expands and contracts axially inresponse to the temperature sensed by a liquid filled tube 194 connectedbetween bellows 193- and temperature unit 50. The tube 194 and a similartube portion 195 connected between temperature unit and bellows 190 areresponsive to the same ambient temperature. However, it is desired tocompensate for the effect of the ambient temperature on tube portion 195such that output motion of arm 186 is a function of compressor inlettemperature T1 only. To this end, the effect of tube 194 which respondsto the ambient temperature and not to compressor inlet temperature T1serves to compensate for the effect on tube 195 as will be desc'nibedhereinafter. A preload against bellows 193 is maintained by a spring196. A `spring 197 interposed between casing 77 and arm 1186 serves tobias arm 186 against roller 1-87.

The cam follower 106 which engages contoured portion 99 of the secondcam is pivotally secured to a yoke 198 which :rotatably carries a roller199. The roller 199 rolls between one arm of a lever 200 and cross arm201 of a T-shaped lever 202 which is pivotally secured to casing 77 Theopposite end of the T-shaped lever 202 is pivotally secured to themovable end of a bellows 203 which is adjustably secured to casing 77 atits opposite fixed end by a threaded extension 204 threadedly engagedwith casing 77. The bellows 203 responds to compressor dischargepressure Pc which is fed to a chamber 205 surrounding bellows 203 via apassage 206. The load applied to lever 200 through roller 199 is opposedby a constant reference force derived from a spring 207 interposedbetween a plate 208 and a spring retainer 209, the latter beingsupported by discs 210 which, in turn, a-re supported by a fixed supportmember 211 threadedly secured to casing 77 The discs 210 provide fortemperature compensation of the fuel surrounding spring 267. The forceof spring 207 is transmitted to lever 200 through roller 199 which rollsbetween plate 208 and the adjacent arm of lever 200 and which isrotatably carried on a yoke 212 pivotally secured to end portion 86 ofmetering valve 34.

A compressor pressure limiting device generally indieated by numeral 213serves to limit the compressor discharge pressure PC to a predeterminedmaximum value. The pressure limiting device 213 includes a bellows 214vented interiorly to passage 206 upstream from a restriction 215 via arestriction 216 and exposed exteriorly to atmospheric air pressure Pa.in a chamber 217. The bellows 214 is loaded in compression by a spring218 which bears against a spring retainer 219 fixedly secured to theclosed end of bellows 214. A lever 22) pivotally secured at one end tocasing 77 `is pivotally secured to spring retainer 219 such thatexpansion or contraction of bellows 214 results in pivotal movement oflever 220 about its one end. The opposite end of lever 221i is adaptedto engage the discharge end of a passage 221 leading from passage 206downstream from restriction 215 to chamber 217 at atmospheric airpressure Pa.

Fuel at regulated servo pressure Pr is delivered to the afterburner fuelcontrol 55 at a predetermined high pressure air compressor speed N2 viaa passage 226 connected to passage 181, a slide valve 227, and a passage228. The slide valve 227 is biased to a closed position by a spring 229as shown in FIGURE 2, such that ow from passage 226 to passage 228 isblocked and passage 228 is vented to the interior of casing 77 at drainpressure Po. A lever 230 pivotally secured to an adjustable fixed rod231 threadedly engaged with casing 77 and pivotally secured to slidevalve 227 is adapted to be engaged by an arm 232 xedly secured to piston105. At a predetermined position of piston 105 which corresponds to apredetermined high pressure air compressor speed N2, the lever 230 isactuated by arm 232 causing slide valve 227 to move upward againstspring 229 thereby communicating passage 226 with passage 228 to permitfuel at regulated servo pressure Pr to flow to the afterburner fuelcontrol 55.

The speed request cam 132 is actuated axially on shaft 133 as a functionof compressor inlet air temperature Ti and pressure Pi by either of twocams 233 or 234 which are contoured radially as a function of compressorinlet air temperature Ti and axially as a function of compressor inletair pressure Pi. The cams 233 and 234 are fixedly secured together andare slidably carried on a shaft 235 having a pinion 236 fixedly securedthereto which meshes with rack 176. The cams 233 and 234 rotate withshaft 235 and are translated on shaft 235 by a follower 237 pivotallysecured to casing 77 and provided with an end portion which extends intoan annular recess 238 separating cams 233 and 234. The opposite endportion of follower 237 extends into an annular recess 239 formed in apiston mem-ber 240 slidably carried in a -chamber 241. Fuel at regulatedservo pressure P1. is conducted via a passage 242 fro-m passage 181 tochamber 241 at one side of piston 240 from which the fuel flows througha restriction 243 fixedly secured to piston 240 to chamber 241 at theopposite side of piston 240 from which the fuel flows to the interior ofcasing 77 at drain pressure Po via a passage 244 having a variable areavalve 245 at the discharge end thereof. The effective flow area of valve245 and thus the pressure drop across piston 246 is controlled by alever 246 pivotally secured to casing 77 and provided with an endportion which extends into a chamber 247 and which is pivotally securedto the movable end of a sealed bellows 248. A fixed end of the bellows248 is adjustably `anchored to casing 77 by screw member 249 threadedlyengaged with casing 77. The bellows 248` expands or contracts inresponse to a decrease or increase, respectively, of compressor inletair pressure Pi which is supplied to chamber 247 via a passage 250. Theforce applied to lever 246 by bellows 248 is opposed by a constantreference force derived from a spring 251 and transmitted to lever 246through a roller 252 which rides between a plate 253 against whichspring 251 Ibears and an arm 254 integral with lever 246. The roller 438is rotatably carried by a yoke 255 which is pivotally secured to piston240. A spring retainer 256 supported by temperature responsive discs 257serves to retain the one end of spring 251.

The cam 132 is actuated axially by a lever 258 having an end portionwhich extends into an annular recess 259 formed at one end of cam 132.The lever 258 is integral with a casing 260 having a chamber 261 inwhich a piston 262 is slidable. The casing 260 is pivotally supported oncasing 77 by a cylindrical extension 263 integral with casing 260 andpivotally secured in a bore 264 in casing 77 and is provided withintegral parallel arms 265 and 266. Arm 265 is loaded by a spring 266which urges casing 260 counterclockwise. Lever 268 is pivotally securedto arm 266 and the lever and arm are provided with cam followers 269 and270, respectively, secured thereto which are adapted to engage cams 233and 234, respectively. As shown in FIGURE 2, the cam follower 270 isheld away from cam 234 when cam follower 269 is engaged with cam 233.However, under certain conditions of operation the cam follower 269 isheld away fro-m cam 233 and cam follower 270 is permitted to engage cam234. In either event, it will be understood that only one of the cams233 and 234 is effective at any given time depending upon which of thefollowers 269 and 270 is engaged with its respective cam surface. Tothis end, the lever 268 is attached at one end to one end of a tensionspring 271 which is attached at the opposite end to arm 265. A roller272 rotatably carried by a yoke 273 is engageable with o-pposingsurfaces of arm 265 and lever 268. The yoke 273 is pivotally secured topiston 262. A'spring 274 interposed between piston 262 and casing 260opposes regulated servo pressure Pr which is transmitted to chamber 261via a passage 275 leading to the bore 264, a central passage 276 inextension 263 and a passage 277 in casing 260. A restricted passage 260communicates passage 275 with the interior of casing 77 at drainpressure P0.

The spring loaded valve 82 is vented on its back side to fuel at drainpressure Po or fuel at pump discharge pressure P1 via a passage 278, aspring loaded slide valve 279 and a passage 280. The slide valve 279 ispressure balanced and biased to the position shown `in FIGURE 3 by thespring bearing thereagainst whereby passage 278 is vented to drain fuelpressure P0. A lever 281 xedly secured to shaft 133 engages slide valve279 at a fuel cutoff position of throttle lever 54 and actuates valve279 to thereby establish communication between passages 278 and 280 andpermit fuel at pressure P1 to ilow to the back side of valve 279. Thespring force acting against valve 82 assisted by fuel pressure P1overcomes the fuel pressure P2 acting against the opposite side of valve82 thereby actuating valve 82 to a closed position which results inshutting off the fuel flow to conduit 44.

The fuel pressure drop Pl-Pg across metering valve 84 is maintained at apredetermined value by a by-pass valve 282 which controls the effectiveflow area of a fuel by-pass conduit 283 leading from passage 78 to thedrain passage 53. A piston 284 integral with by-pass valve 282 isslidable within a chamber 285 and is exposed on one side to fuelpressure P2 which is supplied to chamber 285 via a passage 286 having .arestriction 287 therein. The opposite side of piston 284 is exposed toservo fuel pressure Ps derived from fuel pressure P1 and supplied tochamber 285 via a passage 288, a chamber 289, and a passage 290. Theservo fuel pressure Ps is controlled by a valve 291 connected to theinlet end of passage 290 and arranged to vary the effective flow areathereof in response to movement of a lever 292 pivotally connected tocasing 77. Lever 292 is pivotally connected tto and actuated by theclosed end of a bellows 293 which is exposed on one `side to fuelpressure P1 in chamber 289 and on the opposite side yto fuel pressure P2in a chamber 294 which communicates with chamber 285 via :a passage 295.A predetermined spring load is imposed on bellows 293 by a spring 296supported by temperature responsive discs 297 and adjustable retainer298 threadedly `secured to casing 77. A spring 299 interposed betweencasing 77 and piston 284 loads the by-pass valve 282 in a closingdirection. A spring 300 interposed between piston 284 and a piston 301slidably carried 'by valve 282 loads the piston 284 in opposition tospring 299. The load derived from spring 300 varies depending upon theposition of piston 301 which responds to the fuel pressure differentialP1P2 thereacross. A restricted passage 302 communicates passage 290 withpassage 78 at fuel pressure P2. It will be noted the piston 301 -coactswith the Valve 282 such that the effective How area of valve 282ldepends upon the position of piston 301 as well as the position ofvalve 282. For further details of structure and operation of the by-passvalve 282, reference is made to copending application Serial No.782,948, filed December 24, 1958, in the name of F. R. Rogers et al.(common assignee).

An emergency fuel schedule is supplied to conduit 44 in the event of amalfunction of the above described structure of the main fuel control43. To this end, a spring loaded fuel transfer valve 303 slidablycarried in casing 77 is arranged to divert fuel from passage 78 upstreamfrom filter 79 to a conduit 304 leading to passage 44 and provided witha variable area valve 305 which controls the effective flow areathereof. The valve 305 is pivotally connected to a lever l306 which, inturn, is fixedly secured to and rotated by a gear 307 which meshes withgear 134 .and is positioned .as a function of throttle lever 54position. The fuel pressure differential across valve 305 is regulatedby a double ported by-pass valve 308 which controls fuel ow through afuel by-pass conduit 309 leading from conduit 304 yto the conduit 283 atdrain pressure P0. A diaphragm 310 xedly secured to valve 308 and loadedby `a spring 311 supported by adjustable retainer 312 threadedly engagedwith casing 77 is responsive to fuel pressure P1 upstream from valve 305and a servo fuel pressure Ps derived from fuel pressure P1 andregula-ted by a valve 31-3 upstream from a xed area restriction 314. Thevalve 313 and restriction 314 are arranged in series in a conduit 315leading from con duit 309 to conduit 304. The fuel pressure Psintermedi- `ate Valve 313 and lrestriction 314 varies as a function ofthe area yratio of valve 313 and restriction i314 which area ratiodepends upon the position of valve 313. The valve 313 is slidablycarried in casing 77 and is actuated by one end of a lever 316 pivotallysecured `to casing 77. The opposite end of lever 316 -is pivotallyconnected to the movable end of a sealed bellows 317 which is anchoredat its opposite end to casing 77 by an adjustable retaining member 318threadedly engaged with casing 77. Compressor inlet air pressure P1 issupplied Va a passage 319 leading from passage 49 to a chamber 320surrounding bellows 317 lwhich expands and contracts in response to adecrease and increase, respectively, in pressure Pi. The transfer valve303 is held in the position shown in FIGURE 2 by a spring 321 which isassisted by fuel pressure P1 in a chamber 322 containing spring 321. Thechamber 322 receives fuel from conduit 78 via a restricted passage 323in one end of valve 303 and is vented to by-pass conduit 309 at drainpressure Po via a passage 324 containing a normally closed valve 325which is actuated by an electrical solenoid 326. The opposite end ofvalve 303 is exposed to fuel pressure P1 in a chamber 18 whichcommunicates with conduit 78 via a passage 19 formed in Valve 303. Thesolenoid 326 is energized by switching means which may be manuallyactuated or automatically actuated in response to a malfunction of themain control system heretofore described. Energization of the solenoid326 causes valve 325 to open whereupon the fuel pressure in chamber 322decreases to drain pressure Po by virtue of the pressure drop acrossrestricted passage 323 which allows fuel pressure P1 acting against theone end of valve 303 to overcome Ispring y321 thereby displacing valve303 to the right to cut off oiw through conduit 78 and simultaneouslydivert ow from conduit 78 to con-duit 304. A spring loaded check valve327 in conduit 304 is held closed by fuel pressure P2 `downstreamtherefrom during normal operation. Under emergency operation the checkvalve 327 is open and the check valve 83 in conduit 78 is held closed bythe fuel pressure downstream therefrom.

Referring to FIGURES 4, 4a and 5, numerals 328 and 329 designate casingsof the afterburner fuel control 55 and exhaust nozzle control 70,respectively. A passage 330 vents the interior of casing 328 to theinterior of casing 329 which, in turn, is vented to conduit 53 at drainpressure Po via passa-ge 63.

Referring to FIGURES 4 and 4a, the centrifugal pump 60 is arranged todischarge into a conduit 331 which contains a check valve 332 and apressure regulating valve 333 and which leads to Ithe inlet of 1ametering valve 334 from which fuel flows through `a throttling valve 335to a conduit 336 leading to conduit 56 which, in turn, supplies fuel tovafterburner manifold 38. A pressure regulated valve 337 and fuelcut-off valve 338 are arranged in series flow relationship in conduit336. The remaining two afterburner manifolds 39 and 40 are supplied fuelvia separate conduits 339 and 340, respectively, leading from conduit331 to valve structure, not shown, identical to metering valve 334,throttling valve 335, pressure regulating valve 337 and cut-off valve338 and designated by boxes 341 and 342, respectively, whichcommunicates with outlet conduits 57 and 58 leading to afterburnermanifolds 39 and 40, respectively.

A pressure .actuated valve 345 in conduit 59 leading to the inlet ofpump 60 -is actu-ated to an open position by regulated Afuel pressure Prwhich :is supplied thereto via a passage 346 leading lfrom the main fuelcontrol 43 to the exhaust nozzle control 70, a passage 347 is casing329, a passage 348 connecting Ipassage 347 with casing 328, `a passage348 leading to the inlet of a valve 34-9 from which the `fuel :atregulated pressure P,t flows via passage 350 to yvalve 345. rPhe valve349 is provided with an integral piston 351 having an annular area atone end exposed to passage 348 at regulated pressure Pr and an oppositeend exposed fno fuel pressure in la chamber 352. The chamber 352 isvented to regulated fuel pressure Pr via a passage 353 leading frompassage 348 and to drain fuel pressure Po via a passage 354 leading tothe i-nterior 'of casing 328 at pressure P0. As shown in FIGURE 4, thepiston 351 is `biased against a stop 355 integral with casing 328 byregulated pressure Pr in :opposition to the force tof a spring 356interposed between stop 355 and piston 35.1. A flapper valve 357engageable with orifices 358 and 359 in series flow With passages 353and 354, respectively, is attache-d `to 'one end of a lever 360 which ispiv-otally secured to casing 328 and which is pivotally secured at itsopposite end to a stem 361 Ifixedly secured to a diaphragm 362. Thediaphragm 362 is loaded by -a `spring, 363 and is vented on :one .sideto conduit 331 upstream yof check valve 333 via passage 364 and on theopposite side to Iconduit 331 downstream of check valve 333 via apassage 365. A passage 365 containing a restriction 366 Iis connectedbetween passages 364 and 365. A spring 367 interposed between piston 351and lever 360 serves to preload lever 360. Movement of piston 351results in a correspon-ding change in spring 367 load against lever 360thereby causing flapper valve 357 to move to a fully open `or closedposition 'depending rupon the `direction of movement of piston 351.

The centrifugal pump 60 Iis a Irelatively high capacity pump and :doesnot therefore function eiiciently at relall ll tively low flow rates.The initial low fuel ow rate for afterburner operation is supplied bythe engi-ne driven positive displacement type pump 76 which alsosupplies pressurized fuel to the exhaust nozzle control 70 (FIG- URE T-othis end, -fuel tis supplied to conduit 331 from the pump 7-6 va aconduit 368 containing a filter 369 and a spring loaded pressureregulating vlalve 370 (FIGURE 5), a passage 371 leading to the inlet ofa valve 372 from which fuel flows through a passage 373 to conduit 331upstream from check valve 333. The pressure regulating v-alve 370functions to reduce the :relat-ively high pressure fuel which may be onthe order 3,000 psi. discharged by pump 76 to a lower pressure such as1,000 p.s.i. which is supplied to conduit 371. The valve 372 has asmaller area portion 374 exposed to the fuel pressure in passage 371,and is provided with a piston portion having a-n annular portion 3-75which is exposed to drain fuel pressure P(J via -a passage 376, and alarger area portion 377 expose-d -to the fuel pressure in conduit 331upstream yfrom check valve 332 via a passage 378.

The variable area meter-ing valve 334 in flow controlling relationshipwith conduits 331 and 336 is provided with a piston portion 379 which isslidably carried by casing 328 and which separates varia-ble volumechambers 380 and 381. Filter-ed =fuel is supplied to chamber 380 fromconduit 331 via a passage 382 containing a filter 383. A branch passage384 4containing a restriction 385 communicates passage 382 with chamber381. The metering valve 334 is positioned in accordance with the servopressure PX in chamber 381 which `is controlled by a Servo valve 386which coacts with the inlet end of an axial passage 387 formed in valve334 to vary lthe flow out of chamber 381. A spring 388 'interposedbetween piston portion 379 and casing 328 and a spring 389 interposedbetween servo valve 386 yand piston portion 379 provide lopposi-telyacting preloads on valve 334. The servo valve 334 is positioned towardor away from passage 387 by a lever 390 pivotally secured at lone end toan extension 391 of valve 334 which extension is slidably carried .bycasing 328. An adjustable stop 392 threadedly engaged with lever 390 isadapted to engage casing 328, thereby limiting movement of leve-r 390.The lever 390 is iixedly secured to a shaft 393 which is journalled incasing 328 an-d which slid-ably carries a follower 394 having a lian-ge395 formed thereon. A rod 396 xedly secured to lever 390 is slidablycarried in a slot 397 in flange 395 tto thereby permit follower 394- tomove axially relative to lever 390 but prevent relative rotationalmovement therebetween. The follower 394 is provided with `an adjustablearm 398 threadedly engaged therewith and yadapted to engage a cam orramp member 399 pivotally secured to casing 328 by means of a shaft 400.A follower 401 threadedly engaged with cam member 399 rides against athree :dimensional cam 402 fixedly secured to la shaft 403 suit-ablysupported by lcasing 328 for rotational and axial movement. The shaft403 is translated by a lever 404 pivotally secured to casing 328 andextending intro engagement with a retainin-g annulus 405 formed on shaft403. The opposite end portion of lever 404 is pivotally secured to Iaservo piston 406 which responds to a variable servo fuel pressuredifferential Ps-Pr thereacross. The fuel pressure PS-Pl. is controlledby a servo valve 407 which regulates the fuel pressure PS and which isconnected tio one en-d yof a lever 408 pivotally secured to casing 328.The lever 408 is actuated by a bellows 409 having one end anchored tocasing 328 'and an opposite closed end which bears :against one end oflever 408. A spring 410 urges lever 408 i-nto engagement with the`closed end of .bellows 409. A tube 411 filled with a temperatureresponsive liquid .is connected at one end to temperature probe 61 andat an opposite end to the `interior of bellows 409 which, like tube 411,is lilled with temperature responsive liquid. The -bellows 409 expandsor contracts -by virtue of the volume expansion or contraction of thetemperature responsive liquid in response to temperature variations atprobe 61. The shaft 403 is rotated by a rack 412 (see FIGURE 5) whichengages a pinion 413 xedly secured to shaft 403 and which forms par-t ofthe control mechanism of the exhaust nozzle control 70 to be described.It will be understood that the shaft 403 is transl-ated as la function`of compressor inlet temperature Ti and rotated by rack 412 as afunction of exhaust nozzle area, pressure ratio PT4/PT7 `across turbines33 and 30 and the position of throttle lever 54.

The follower 394 is translated on shaft 393 by a lever 414 pivotally:secured to casing 328 and engageable at one end with a ange 395integral with follower 394. A spring 415 interposed between lever 390and foll-ower 394 serves to bias flange 395 into engagement with thea-djacent end of lever 414. The remaining two followers 394 connected tovalve structure 341 and 342, respectively, likewise are provided withsimilar structure as shown in FIGURE 4a where the followers 394simultaneously respond axially to movement of lever 414 and rotateindependently of each other to position the respective control levers390 to a variable degree depending upon the contour tof the respectivecams 402, 451 and 452. The opposite end of lever 414 extends intoengagement with a retaining annulus 416 `formed in an extension of aservo piston 417 slidably carried in casing 328 and responsive to a fuelservo pressure differential Ps-Pr thereacross. The pressure differentialPs-Pr is controlled by a servo valve 418 which regulates `fuel pressurePs in response to movement of a lever 419 pivotally secured to casing328. The lever 419 is actuated by a bellows 420 which is anchored at oneend to casing 328 and vented interiorly to compressor discharge pressurePc via passage 62. An evacuated bellows 421 is xedly secured at Ione endto casing 328 and at its opposite end is xedly secured to bellows 420which, in effect, renders the output force of bellows 420 a function ofcompressor discharge pressure PC absolute. A feedback torque is appliedthrough lever 419 in `opposition to the torque derived from bellows 420thro-ugh a roller 422 which rides between lever 419 and a plate 423loa-ded by a constant reference force derived from a spring 424. One endof spring 424 is supported by temperature responsive discs 425 andadjustable retaining member 426 threadedly engaged with casing 328. Theroller 422 is rotatably secured to a yoke 427 pivotally secured to servopiston 417 and is positioned simultaneously with movement of servopiston 417 to vary the effective lever arm 4of lever 419 through whichthe constant reference force spring 424 acts to thereby balance theopposing torque derived from bellows 420. The temperature responsivediscs provide temperature compensation with regard to the fuelsurrounding spring 424.

The fuel pressure differential P1-P2 across metering valve 334 iscontrolled at a predetermined constant value by throttling valve 335 inseries with and downstream from metering valve 334. A piston 429integral to valve 335 is provided with a relatively large face 430against which a servo -fuel pressure PX acts, an intermediate face 431to which fuel at pres-sure P1 is supplied via a passage 432 leading frompassage 382, and a relatively :small face 433 which further includesannular end portion 434 against which fuel at pressure P2 acts. Theservo fuel pressure PX is generated 'between a restricted inlet passage435 leading from passage 382 and a. discharge passage 436 having avariable area valve 437 arranged in the discharge end thereof. The flowout of passage 436 and thus pressure PX is controlled by valve 437 whichis connected to the movable end of a bellows 438 exposed on one side tofuel pressure P1 via a passage 439 leading from the upstream side ofmetering valve 334 and exposed on the opposite side to fuel pressure `Pzvia a passage 440 leading from the downstream side of metering valve334. The fuel pressure differential Pl-PZ acting across bellow-s 438 isopposed by a spring 441 interposed between an adjustable spring retainer442 threadedly secured to casing 328 and a spring retaining member 443fxedly secured to the movable end of bellows 438. The lbellows `438 isanchored at its open end to casing 328 by any suitable means providing afluid seal.

The cut-off `valve 338 is responsive to metered fuel pressure P3 inconduit 336 and to a spring `444 and fuel pressure in a chamber `445which receives fuel :from conduit 336 via a passage 446 in :parallelwith check valve 337 and rest-ricted passages 447 and 448. A dischargepassage 449 conducts lfuel out of chamber 445 and the flow therethroughis controlled by a valve in the exhaust nozzle control 70 to bedescribed. A filter 450 disposed in passage 446 serves to filter thefuel received by passages 447 and 448.

As pointed out heretofore, the afterburner fuel control 55 cont-rols theflow of fuel to three afterburner fuel manifolds 38, 39 and `40. Theabove described metering valve 334, throttling valve 335, cut-off valve338, pressure regulating valve 337 are duplicated for each of the othertwo manifolds 39 and 40 and `designated by boxes 341 and 342,respectively. The operation of the .metering valve 334 in the boxes 341and 342 is controlled by cams 451 and 452, respectively, which, like cam402, are carried by shaft 403 and rotated and translated as a functionof cornpressor inlet temperature T1 and exhaust nozzle area, pressure-ratio Dm/PT, across turbines 33 and 30, and throttle lever 54 position,respectively, As in the case of cam 402, cams 451 and 452 each actuate afollower 401 connected to a cam member 399 pivotally secured to casing328. The cam member 399 in each case actuates a followe-r 394 which, inturn, rotates a lever 390 fxedly secured to an associated shaft mountedfor rotation in casing 328 which lever 390 is connected to control theoperation of its associated metering valve 334.

Now, referring to FIGURES 5 and 6, which together illustrate the exhaustnozzle control 70 in more detail, the conduit 368 is connected to apassage 453 leading to the inlet of a spool valve 454 which is shown ina null position whereby lands 455 and 456 thereof block passages 457fand 458, respectively, which lead to passages 66 and 68 communicatingwith piston 65. Movement of spool valve 454 in one direction from thenull position shown serves to simultaneously communicate passage 457with passage 453 and communicate passage 458 with drain fuel pressure Povia drain passage 459 leading to fuel conduit 76, whereas movement inthe opposite direct1on communicates passage 458 with passage `453 andcommunicates passage 457 with drain fuel pressure Po via drain passage460 leading to drain passage 459. A servo piston 461 integral with spoolvalve 454 is provided with an extended portion having a passage 462therein which 1s in series with a passage 463 leading from one side ofservo piston 461. The opposite side of servo piston 461 communicateswith regulated fuel pressure in passage 371 via a passage 464. A springloaded check valve 465 communicates passage 371 with drain passage 459and opens when the pressure of the fuel in passage 371 exceeds apredetermined value. A restricted passage 466 permits fuel to flow frompassage 464 to passage 463. A solenoid operated valve 467 disposed inpassage 463 is biased to a closed position in response to energizationof the solenoid 467' attached ,thereto to thereby prevent flow throughpassage 463. With valve 467 in an open position the fuel pressure on oneside of piston 461 is controlled by a valve member 470 which coacts withthe discharge end of passage 462 to vary the effective flow areathereof. The valve 470 is attached to one end of a lever 471 which, inturn, is pivotally secured to one end of a rod 472 and actuated by afollower 473 fxedly secured thereto. The follower 473 rides against afirst contoured portion of a three dimensional nozzle area and fuel flowcorrelation cam 474 fxedly secured to a shaft 475 mounted on casing 329for rotational and axial movement relative thereto. The shaft 475 is ro-14 tated as a function of exhaust nozzle area by pulley 74 through gearsgenerally indicated by 476. The shaft 475 is translated las la functionof the pressure ratio PT4/PT7 across turbines 33 and 30 by a lever 477pivotally connected at one end to shaft 475 and pivotally connected toan extension 478 integral with a servo piston 479. Fuel at regulatedservo pressure Pr is supplied to one side of piston 479 at apredetermined high pressure compressor speed N2 from main fuel control43 via a passage 480, a spring loaded spool valve 481 actuated by afirst contoured portion of a cam 482, a passage 483, a twoposition spoolvalve 484, and passage 228. The piston 479 is provided with arestriction 486 which communicates the one side of piston 479 with theopposite side thereof from which opposite side the fuel escapes to theinterior of casing 329 at drain pressure Po via discharge passage 487.The pressure drop across the piston 479 is controlled by a servo valve488 secured to one end of a lever 489 pivotally secured to a stem 490which is fxedly secured at one end to the movable end of an evacuatedbellows 491 and which is fxedly secured at the opposite end to themovable closed end of a bellows 492. The evacuated bellows 491 isanchored at one end to casing 329. The bellows 492 is anchored at oneend to casing 329 and is vented interiorly to pressure PT4 upstream ofturbine 33 via passage 72. The lever 489 is pivotally secured to casing329 at 494. A roller 495 rides against lever 489 and :across an tarmintegral with a lever 496 which is pivotally secured to casing 329 and astem 497. The stem 497 is fixedly secured at one end to the movable endof an evacuated bellows 498 and at its opposite end to the movableclosed end of a bellows 499. The evacuated bellows 498 is anchored atone end to casing 329. The bellows 499 is anchored at one end to casing329 and is vented interiorly to pressure PT7 downstream of turbines 30via passage 73. The roller 495 is rotatably carried by a yoke 501pivotally secured to a spring loaded follower 502 which is slidablycarried by casing 329 and which is biased into engagement with the rstcontoured surface of the three dimensional cam 482. The cam 482 ismounted on a shaft 503 which rotates the cam 482 and which is providedwith an integral pinion 504. A rack 505 fxedly secured to a servo piston506 drives the pinion 504 in response to movement of piston 506. The cam482 is slidably mounted for axial movement on shaft 503 and istranslated by a yoke 507 fxedly secured to extension 478 and suitablysecured to an annulus on the cam 482 to permit rotational movementthereof. Fuel at regulated pressure Pt is conducted to one side ofpiston 506 via a passage 508 leading from passage 483. Fuel istransmitted through a restriction 509 in piston 506 to the opposite sideof piston 506 from which fuel flows through a passage 510 to the mainfuel control 43 (FIGURE 2). Referring to FIGURE 2, the passage 510discharges into a chamber S11 which is vented to the interior of casing77 at drain pressure `P0 via a passage 512. A valve 513 connected to thedischarge end of passage 510 serves to control the effective flow areathereof and thus servo pressure PX on the one side of piston 506. Alever 514 pivotally secured to casing 77 is actuated by the movable endof a bellows 515 having a fixed end anchored to casing 77. A restriction516 fxedly secured to the movable end of bellows 515 permits fuel toflow out of bellows 515 to chamber 511 at drain pressure P0. A roller517 rides between lever 514 and a plate 518 which is loaded by aconstant reference force derived from a spring 519 having a fixed endsupported by an adjustable retainer 520 threadedly engaged with casing77. The roller 517 is rotatably connected to a yoke 521 which ispivotally secured to a follower 522 slidably carried by casing 77 andengageable with cam portion 101. The interior of bellows 515 is ventedto the interior of a bellows 523 in exhaust nozzle control 70 (FIGURE 6)via a passage 524. Referring to FIGURE 6, restricted passage 525communicates fuel at regulated pressure P,t to passage 524 from passage483. The fuel flow out of passage 524 and thus fuel pressure Ps withinbellows 515 is controlled by a servo valve 526 iixedly secured tothemovable end of bellows 523 which coacts with the inlet end of a tubularmember 527 xedly secured to a fixed end of bellows 523 and communicatingthe interior of bellows 523 with the interior of casing 329 at drainfuel pressure P0. The movable end of bellows 523 is xedly secured to alever mechanism 528 which is loaded by a constant reference forcederived from a spring 529 acting through a roller 530 which ridesbetween lever 528 pivotally secured to casing 329 and a plate 531against which spring 529 bears. The opposite end of spring 529 issupported by an adjustable retainer 532 threadedly engaged with casing329. The roller 530 is rotatably carried by a yoke 533 pivotally securedto rack 505. A lever 528 pivotally secured to casing 329 and spaced fromlever 528 is adapted to engage an end portion of lever 528 as will bedescribed hereinafter. Levers 528 and 528 are preloaded by springs 534and 535, respectively, which are supported at one end by adjustableretainers 536 and 537, respectively, threadedly engaged with casing 329.A bellows 538 provided with a movable closed end is engageable withlever 528 and is anchored at its opposite end to casing 329 and isvented interiorly to passage 483 at regulated pressure Pr via arestricted passage 539 and to the interior of casing 329 at drainpressure Po via a passage 540 leading from passage 539 upstream of therestriction therein to a passage 541 formed in a lever member 542 andprovided with a servo valve 543 at the discharge end thereof. The levermember 542 is pivotally mounted to casing 329 at 544. A rotatable cam545 fixedly secured to a shaft 546 which is rotated by throttle lever 54engages servo valve 543 and holds the same closed until a predeterminedthrottle lever position is attained at which time the servo valve 543 isallowed to open thereby venting passage 541 to drain pressure P0. Alever 547 pivotally secured a-t one end to lever member 542 andpivotally secured at its opposite end to a ratchet member 548 is biasedinto engagement with a stop member 549 on lever 542 by a spring 550interposed between lever 547 and a retainer 551 fixedly secured to lever542. A spring 552 interposed between casing 329 and lever 547 urgeslever 542 toward cam 545. The ratchet member 548 is provided with a stop553 integral thereto which is urged into engagement with lever 547 bythe force of a spring 554 interposed between lever 547 and ratchetmember 548. A servo valve 555 xedly secured to lever 547 coacts with thedischarge end of a passage 556 formed in an extended portion of a servopiston 557 which is vented on one side to regulated fuel pressure l)rvia a passage 558 leading from passage 346 and on the opposite side tofuel at regulated pressure Pr via a restricted passage 559, a passage560 leading to the outlet side of a spool valve 561, and a passage 562leading from the inlet side of valve 560 to passage 483. A valve member563 integral to servo piston 557 is provided with a passage 564 which`serves to connect a passage 565 leading from passage 560 at regulatedpressure P1. with a passage 566 leading to passage 275 in the main fuelcontrol 43 (FIGURE 2) which, in turn, leads to chamber 261 at one sideof piston 262. A second passage 567 in valve member 563 serves toconnect a passage 568 leading from passage 565 at regulated pressure P1.with one of three spaced apart passages 569, 570 or 571 depending uponthe position of the valve 563. The passages 569, 570 and 571 merge intoa passage 572 leading to one side of a two position piston 573 where itacts in opposition to a spring 574 bearing against piston 573. A branchrestricted passage 575 communicates passage 572 with the opposite sideof piston 573 from which fuel is permitted to escape to the interior ofcasing 329 at drain pressure P0 via a passage 576 formed in piston 573and a servo valve 577 engageable with the dis` charge end of passage576. The servo valve 577 is xedly secured to one end of a lever 578pivotally secured to Casing 329 and provided with an adjustable screwmember 579 threadedly engaged therewith which is engaged by a bracket580 txedly secured to extension 478. A spring 581 loads lever 578 in acounterclockwise direction. The piston 573 is provided with an integralvalve portion 582 which in oneposition communicates a passage 583leading from passage 480 at regulated pressure 1:'r with a passage 584leading to one side of a spring loaded piston 585 which is exposed onits opposite side to drain fuel pressure Po and in a second position, asshown in FIGURE 5, disestablishes said communication and vents passage584 to drain pressure P0. A stem 586 extending from piston 585 isengageable with one end of a spring biased lever 587 pivotally securedtocasing 329 which lever is provided with an opposite end portion 588engageable with upper ats of ratchets 589, 590 and 591 formed on ratchetmember 548. A springbiased lever 592 is pivotally secured to casing 329is provided with an end portion 593 engageable with lower flats ofratchets 589, 590 and 591 and is adapted to be engaged by a stem 594integral with a spring biased piston 595 having a restriction 596 whichprovides for drainage of fuel from one side of piston 59S to theopposite side thereof. Fuel at regulated pressure Pr is supplied to oneside of piston 595 via a passage 597, and a passage 598 leading frompassage 347. A valve 599 in flow controlling re1ation ship with passage597 is pivotally secured to a lever 600 which is pivotally secured tocasing 329 and actuated by raised portions 601, 602 and 603 formed on anextension of rack 412. The rack 412 is actuated by servo piston 604 oneside of which is exposed to regulated pressure Pr via passage 605leading from passage 598. The opposite side of servo piston 604communicates with regulated pressure Pr via a restricted passage 606leading from passage 568 and with the interior of casing 329 at drainpressure Po via a discharge passage 607 formed in an extension 608integral with piston 604. The flow through passage 607 and thus Ithefuel pressure acting upon piston 604 is controlled by a servo valve 609which coacts with the discharge end of passage 607 to vary the effectiveflow area thereof. The servo valve 609 is xedly secured to and actuatedby a follower 610 which rides against a second contoured portion of cam474. A lever 611 pivotally secured to follower 610 at 612 is resilientlyheld in position relative to follower 610 by a spring 613 interposedbetween follower 610 and spring retainer 614 integral with lever 611. Apair of adjustable stop members 616 and 617 threadedly engaged with alever 615 are adapted to engage lever 611 as will be described. Thelever 615 extends into engagement with a restraining annulus 618 formedon rod 472 which is actuated by a lever 619 pivotally secured at one endto casing 329 and at the opposite end engageable with the end of valve563. A spring 620 serves to bias the end of rod 472 into engagement withlever 619.

An arm 621 lixedly secured to valve 563 is connected to a spool valve622 which is provided with lands 623 and 624. Depending upon theposition of valve 622, land 623 serves to vent passage 449 leading tomanifold cutoff valve 338 to drain pressure P0 as well as passages 625and 626 leading to valves 338 in boxes 341 and 342, respectively. Also,depending upon the position of valve 622, the passage 449 may be ventedto a passage 627 leading from passage 382 which passage 627 contains aflow regulating valve 628. A diaphragm 629 xedly secured to valve 628responds to the pressure drop across valve 628 which acts in oppositionto a spring 630 acting against diaphragm 629 to thereby control theposition of valve 628 to maintain the pressure drop thereacross at aconstant value. With the valve 622 positioned as shown in FIGURE 5, thelshut-off valve 338 is held closed by virtue of the passage 626 beingvented to passage 627 which permits a continuous. flow of pressurizedfuel p drain pressure PD.

`17 through passage 626 to the valve 338. The continuous flow of fuel tovalve 338 also provides for cooling of the same when closed since thevalve 338 may be positioned near the engine in an environment ofrelatively high temperature.

The spool valve 481, FIGURE 6, is provided with a stern 631 whichengages a second contoured surface of cam 482. The valve 481 is actuatedin one direction from a null position shown to vent fuel at regulatedpressure Pr to a passage 632 leading to one side of a servo piston 633and simultaneously vent a passage 634 leading from the opposite side ofpiston 633 to the interior of casing 329 at drain pressure P0. Actuationof valve 481 `in the opposite direction from the null position ventspassage 634 to regulated pressure Pr and passage 632 to The servo piston633 is pivotally secured to one end of lever 477 which is pivoted aboutits connection with extension 478 in response to movement of piston 633.

A fuel pressure signal indicative of .afterburner blow-out is suppliedto the main fuel control 43 from exhaust nozzle control 70 via a passage635 leading to passage 148 downstream of solenoid actuated valve 150(FIGURE 2). As shown in FIGURES and 6, the passage 635 is vented to fuelat regulated pressure P,r via a passage 636, a chamber 637 containing adouble ended valve 638, a passage 639, a spool valve 640 and a passage641 leading to passage 483 at regulated pressure Pr. The valve 638 isshown in a normally closed position whereby the smaller end thereofcooperates with the discharge end of passage 639 to block flowtherethrough. The opposite large end of valve 638 is biased away from anorifice 642 which vents chamber 637 and passage 636 connected thereto tothe interior of casing 329 at drain fuel pressure P0. The valve 638 isheld in the normally closed position by a lever 643 pivotally securedthereto and pivotally secured to casing 329. The opposite end of lever643 is engaged by a spring biased retaining member 644 slidably carriedby casing 329 which retaining member urges :lever 643 clockwise therebyclosing valve 638. Bracket 580 on extension 478 is provided with anadjustable screw member 645 threadedly engaged therewith which inresponse to movement of extension 478 engages retaining member 644urging the same toward casing 329 thereby unloading lever 643 andpermitting valve 638 to open in response to the fuel at pressure l?racting against the smaller end thereof which fuel at pressure Pr fiowsinto chamber 637 and acts against the larger end of valve 638 therebyholding valve 638 open. It will be understood that the larger end ofvalve 638 is seated by the pressure Pr in chamber 637 thereby sealingthe vent to drain pressure PO.

A passage 646 containing a check valve 647 communicates passage 636 withone side of a land portion 648 of spool valve 561. The check valve 647remains closed until actuated by regulated pressure Pr in passage 636 atwhich time fuel at pressure Ilr is permitted to flow through check valve647 to the one side of land portion 648 whereupon valve 561 is actuatedto the right as viewed in FIGURE 6 causing land portion 648 to blockcommunication between passages 562 and 560. In the above mentionedrightward position a second land portion 649 of spool valve 561 ventspassage 560 to a passage 650 leading to the interior of casing 329 atdrain pressure P0. As valve 561 moves rightward, a tapered end portion651 on valve 561 moves out of engagement with the discharge end of apassage 652 thereby admitting a second source of fuel at regulatedpressure Pr to land portion 648. The passage 652 communicates withpassage 346 at regulated pressure Pr via an annulus 653 in valve 484 anda passage 654.

Fuel at regulated pressure Pt may be introduced to passage 646 via apassage 655 containing a spring loaded check valve 656 which passage 655is vented to passage 641 at regulated pressure Pr by a land portion 657of valve 640. The valve 640 is connected to and actuated by a rod 658one end of which rides in a slotted cam member 659 iixedly secured toand rotated by shaft 475. In response to certain conditions of operationof the exhaust nozzle gates 27, the cam member 659 is adapted to actuatevalve 640 to a position whereby land portion 657 vents passage 655 topassage 641 whereupon check valve 656 is opened and fuel at regulatedpressure PJr communicated to passage 646 to cause rightward movement ofvalve 651 in the above mentioned manner.

The two position spool valve 484 is slidable in a bore 666 havingreduced diameter end portions 661 and 662 which receive fuel atregulated servo pressure Pr from passage 654 via annulus 653, a radialpassage 663 and an axial passage 664 in valve 484. The axial passage 664is provided with restrictions 665 and 666 which control fiow to endportions 661 and 662, respectively. The end portions 661 and 662 arevented to the interior of casing 329 at drain fuel pressure Po viapassages 667 and 668, respectively, which are provided with orifices 669and 670 at the discharge ends thereof. A flapper 671 pivotally securedto casing 329 moves in one direction to open orifice 670 and closeorifice 671 and in the opposite direction to close orifice 670 and openorifice 671, The fiapper 671 is actuated by a follower 672 integraltherewith which engages a first contoured portion of a cam 673 fixedlysecured to shaft 546 and rotated by throttle lever 54. The valve 484 isprovided with lands 674 and 675 which, in the position of valve 484shown in FIGURE 6, are positioned to the right of passages 228 and 652,respectively, which permits passage 228 to communicate with passage 483via annulus 676 in valve 484 and passage 654 to communicate with passage652. With valve 484 positioned to the left, lands 674 and 675 blockpassages 228 and 652. respectively. A spring 677 interposed betweencasing 329 and valve 484 imposes a preload on valve 484 urging the sametoward the left. The valve 484 is provided with opposite beveled endportions 678 and 679 which are engageable with their respective endportions 661 and 662 -of bore 660 to thereby disestablish communicationbetween the end portions 661 and 662 and passages 667 and 668,respectively.

Operation of main fuel control Assuming the engine 20 to be operatinginitially at a steady state idle speed, an acceleration to maximum speedwithout afterburner operation is accomplished in the following manner.The throttle lever 54 is actuated to its maximum speed position whichcauses rotation of cam 132 and a corresponding actuation of bell crank129 in a counterclockwise direction as viewed in FIGURE 2 which, inturn, actuates follower 134) and attached rod 131 causing lever 114 topivot clockwise. The clockwise movement of lever 114 results in ballvalve 116 moving toward valve seat 117 thereby increasing fuel pressurePs which drives piston 109 toward the right as viewed in FIGURE 2causing lever 187 to move out of engagement with abutment 111 whereuponfollower 166 is urged into engagement with cam portion 99 by spring 110bearing against lever 167. The follower 186 follows cam portion 99 whichis contoured to provide a predetermined acceleration fuel schedule as afunction of high pressure cornpressor speed N2 and compressor inlettemperature Ti. The follower 166 drives roller 199 toward the left asviewed in FIGURE 2 thereby increasing the effective lever arm of lever288 through which the force derived from bellows 203 acts causing thelever 280 to pivot clockwise against the opposing constant referenceforce derived from spring 207. The resulting increase in area of orifice94 produces a drop in fuel pressure in chamber 89 causing movement ofpiston 87 and attached valve 84 and a corresponding increase in area oforifice 81 which, in turn, results in increased fuel to the combustionchambers 35. The roller 199 moves with valve 84 causing an increase inthe effective lever arm of lever 200 through which the constantreference force derived from spring 287 acts under the inuence ofpressure Pr.

19 thereby balancing the opposing torque derived from bellows 203 actingthrough lever 200 which results in stabilization of piston 87.

As the engine accelerates in response to the increased fuel flow, thecompressor discharge pressure Pc increases and acts against bellows 203causing a corresponding increase in the force applied through roller 199to lever 288 which, in turn, results in a torque unbalance on lever 260and corresponding clockwise movement of the same. As heretoforementioned, clockwise movement of lever 200 results in upward movement ofvalve 84 and a corresponding increase in fuel ow to the combustionchambers 35. The roller 199' follows valve 84 until the effective leverarm of lever 200 through which the spring 287 acts produces a torqueequal and opposite to the opposing torque derived from bellows 203whereupon lever 200 is stabilized. At a predetermined maximum allowablecompressor discharge pressure Pc, the bellows 214 overcomes the force ofspring 218 and actuates lever 220 away from passage 221 to bleed thepressure in passage 206 downstream from the restriction 215 toatmospheric air pressure Pa thereby limiting the air pressure Pc actingagainst bellows 214 accordingly.

As the engine accelerates, the force of centrifugal weights 164increases as a function of engine speed and unbalances lever 158 in aclockwise direction as viewed in FIGURE 2. The resulting increase inarea of valve 157 results in a drop in pressure Ps acting against piston105 which moves to the left as viewed in FIGURE 2 causing shaft 102 andcams secured thereto to rotate as a function of compressor speed N2. Asthe cams rotate, the follower 106 follows the contour of cam portion 99and controls the movement of valve 84 to provide a desired accelerationfuel flow schedule to the combustion chambers 35. The follower 173follows cam portion 100 and actuates lever 172 clockwise as viewed inFIGURE 2 which, in turn, drives roller 167 causing an increase in theeffective lever arm of lever S through which the constant referenceforce derived from spring 165 acts in opposition to the force ofcentrifugal weights 164. Thus, the torque derived from centrifugalweights 164 acting through lever 158 is balanced by an equal andopposite torque derived from spring 165 acting through a variable leverarm of lever 158 which variable lever arm varies as a function ofcompressor speed N2 through movement of piston 105 and cam portion 100.The compressor speed N2 function imposed on cam portions 99 and 100 ismodified as a function of compressor inlet temperature T by piston 175which actuates lever 178 to cause translation of cam portions 99 and100. To this end, the bellows 198 expands with increasing temperature T1and actuates arm 186 counterclockwise as viewed in FIGURE 2 which, inturn, causes movement of lever 185 and a corresponding increase in areaof valve 184. The increase in valve 184 area causes a reduction in fuelpressure Ps acting against the larger area end of piston 175 whichallows piston 175 to move downward The lever 185 follows the piston 175and reduces the area of Valve 184, thereby causing an increase inpressure Ps whereupon piston 175 is stabilized. The lever 178 followsthe piston 175 and translates cam portions 99 and 189 accordingly. Atemperature error may be introduced in the bellows 190 by the tube 195which is likely to be exposed exteriorly to ambient temperaturessignificantly lower or higher than the temperature at the compressorinlet probe attached thereto. To compensate for the ambient temperatureeffect on tube 195, the tube 194 which is not provided with a probeexposed to compressor inlet temperature T like tube 195 but which isexposed to the ambient temperatures extends alongside tube 195 andconnects to bellows 193 which has a volume equivalent to that of bellows190. As the volume of bellows 193 inreases in response to an increase inthe temperature of tube 194, for example, the bell crank 192 is actuatedclockwise as shown in FIGURE 2 causing the roller 187 to move down thebeveled surface 188 of member 189 thereby reducing the effective lengthof cylindrical member 189 an amount equivalent to the axial expansion ofbellows 190 which, like bellows 193, expands in response to theincreased temperature of its tube 195. A decrease in the temperature towhich tubes 194 and 195 are exposed results in counterclockwise movementof bell crank 192 and corresponding movement of roller 187 up thebeveled surface 188 thereby increasing the effective length of member189 an amount equivalent to the axial contention of bellows 190. If theambient temperature to which the tubes 194 and 195 are exposed remainsconstant, the roller 187 will remain in position on beveled surface 188and lever 186 will move in response to expansion of bellows 19t) as afunction of the compressor inlet temperature Ti only.

The three dimensional cams 233 and 234 are rotated by rack 176 as afunction of compressor inlet temperature T1 in response to the actuationof piston 175. The cams 233 and 234 are translated by lever 237 inresponse to movement of piston member 240 as a function of cornpressorinlet pressure P1. To this end, the bellows 248 responds to compressorinlet pressure P1 causing lever 246 to pivot clockwise orcounterclockwise depending upon the relative change in pressure P1. Forinstance, bellows 248 will contract in response to an increase inpressure Pi causing clockwise movement of lever 246 as viewed in FIGURE3 which increases the area of valve 245 causing pressure Is on thelonger side of piston 240 to decrease thereby upsetting piston 240toward the left as viewed in FIGURE 2. The roller 252 follows piston 240thereby increasing the effective lever arm through which the constantreference force derived from spring 241 acts in opposition to thebellows 248. The increase lin effective lever arm results in a torqueequal and opposite to the torque derived from bellows 24S acting throughlever 246 whereupon the lever 246 is stabilized which, in turn,stabilizes the pressure Ps as necessary to hold piston 240 motionless.

The follower 269 is shown in engagement with cam 233 whereas follower270 is shown out of engagement with cam 234. However, during engineoperation in the nonafterburning range as is the case in the engineacceleration under discussion, the chamber 261 is vented to drainpressure Po via restriction 260 by virtue of valve 563 being in theposition shown in FIGURE 5 whereby passages 565 and 566 are blocked toprevent fuel at regulated pressure Pr from flowing to chamber 261. Withpressure Po in chamber 261, the piston 262 and roller 272 attachedthereto are biased to the right by spring 274 permitting lever 268 topivot clockwise under the influence of spring 272 thereby liftingfollower 269 out of engage- Vment with cam 233 and permitting follower270 to engage cam 234. Thus, as the engine accelerates, the cam 132 ispositioned axially by movement of casing 260 in response to the cam 234.

Referring now to the FIGURE 3 and the by-pass valve 282 which maintainsa constant predetermined pressure differential P1-P2 across orifice 81,it will be understood that various conventional fuel by-pass valves maybe substituted therefor. However, the by-pass valve 232 is adapted toeliminate some of the disadvantages of conventional spring loadedby-pass valves which are subject to error due to fluid pressureunbalance thereacross. To this end, the piston 301 reacts to a drop inpressure differential P1P2 occasioned by an increase in area of orifice81 and moves downward to decrease the effective How area of valve 282through which fuel at pressure P1 flows to passage 283 at drain pressurePo thus decreasing the quantity of fuel by-passed. The bellows 293responds to the aforementioned drop in P1-P2 pressure differentialacross orifice 81 and actuates lever 292 to cause an increase in area ofvalve 291 which, in turn, causes an increase in fuel pressure Ps actingagainst piston 284. The

pressure Ps actuates piston 204 and valve 282 integral thereto downwardagainst the resistance of spring 300 and in a closing direction untilthe force derived from the pressure differential Ps-P2 acting againstpiston 234 is balanced by the force of spring 300 at which time theconstant predetermined pressure differential P1-P2 exists across orifice81. It will be noted that the reset action of piston 301 on spring 301eliminates the spring error which would be introduced if the spring 301was fixed at one end and progressively compressed by piston 284 as thefuel pressure P1 and P2 `increased with the differential therebetweenmaintained constant. In the case of an increase in pressure differentialP1-P2 across orifice 81, the abovementioned operation is reversed tothereby increase the by-pass flow as necessary to restore the constantpredetermined pressure differential.

In the event of a malfunction of the aforementioned fuel controlapparatus such that the fuel control functions impressed on meteringvalve 84 do not provide the desired fuel schedule to the engine, theemergency fuel control apparatus is brought into operation by means of amanual request or automatic switching means responsive to a condition ofoperation indicative of said malfunction. In such a case, the solenoid326 is energized causing valve 325 to move to its open position wherebychamber 322 is vented to drain fuel pressure Po which, in turn, createsa pressure drop across restricted passage 323. The valve 303 isunbalanced to the right whereupon the left hand end of valve 303` blockspassage 78 and the right hand end of valve 303 diverts fuel at pressureP1 into conduit 304. The effective fiow area of conduit 304 and thusfuel flow through conduit 304 to conduit 44 which leads to combustionchambers 35 is controlled by the valve 305 in response to movement ofthrottle lever 54. The v-alve 305 is contoured to provide an emergencyfuel fiow schedule which has a relatively large safety mar-gin so as tomaintain a variable power output of the engine as a function of throttlelever 54 position without exceeding predetermined maximum allowablelimits on engine speed, temperatures and/or pressures.

The fue] flow through conduit 304 is modified as a function ofcompressor inlet pressure P1 by the by-pass valve 308 which regulatesthe pressure differential across valve 305. The by-pass valve 308 ispositioned by diaphragm 310 in response to the differential between fuelpressure P1 on the one side of diaphragm 310 and the fuel pressure Ps onthe opposite side -of diaphragm 310 derived from fuel pressure P1, thelatter pressure Ps being controlled by valve 313 in response to bellows317 actuated by compressor inlet pressure P1. The fuel pressure Ps vvaries as a function of the area ratio of valve 313 and restriction 314and, for each position of valve 313, assumes a value intermediate fuelpressures P1 and P2. For a given position of valve 305, the fuelpressure differential P1-P2 will 'be increased in response to anincrease in compressor inlet pressure P1 which acts to collapse bellows317 accordingly causing valve 313 to open thereby causing acorresponding increase in fuel pressure Ps which, in turn, actuatesby-pass valve 308 toward a closed position to effect an increase in fuelpressure P1. The combined forces of spring 311 and p-ressure Ps actin-gagainst diaphragm 310 are balanced by an equal and opposite forcederived from the increased fuel pressure P1 acting against diaphragm 310whereupon by-pass valve 308 is stabilized. A decrease in pressure P1wil] result in a decrease in pressure Ps and a corresponding reductionin fuel pressure P1.

The check valve 327 is urged to an open position in response to flowthrough conduit 304 at which time check valve 83 is urged to a closedposition in response to the spring force applied thereto and fuelpressure P2 downstream therefrom.

The cam portion 98 is contoured to provide a c-am rise which decreasesas a function of increasing speed N2 such that, upon high pressurecompressor speed N2 approaching the requested maximum value, thefollower 113 is displaced causing lever 114` to pivot counterclockwiseas viewed in FIGURE 2. The servo valve 116 follows lever 114 and movesaway from valve seat 117 ca-us ing a drop in pressure Ps whereuponpiston 109 moves to the left accordingly which allows lever 107 toengage abutment member 11. Continued movement of piston 109 to the leftresults in lever 107 pivoting counterclockwise about the point ofcontact with abutment member 111 thereby lifting follower 106 olf camportion 99 and actuating follower 106 away from cam portion 99. Aspiston 109 follows movement of servo valve 116, the lever 107 andattached follower 106 move accordingly until the follow-up motion ofvalve seat 117 relative to servo valve 116 resestablishes the pressureln necessary to balance piston 109 at which time the lever 107 andfollower 106 are stabilized. The movement of follower 106 results inmovement of roller 199 toward the lpivot point of lever 200 and acorresponding reduction in the lever 4arm through which the forcederived from bellows 203 acts. The lever 200 is unbalanced in acounterclockwise direction causing a reduction in area of orifice 94 anda corresponding increase in pressures acting against piston 87 whichactuates valve S4 in a closing direction thereby reducing fuel flow tothe combustion chambers. The roller 109 follows valve 84 causing areduction in the lever arm through which the force derived from spring207 acts thereby stabilizing lever 200 which, in turn, effectsstabilization of valve 84 and thus fuel flow to the combustion chamberssuch that the engine is governed at the requested high pressurecompressor speed N2.

The abutment member 111 may be adjusted toward or away from screw 112 toeffect a corresponding variation in the ratio of lever arms defined bylever 107 coacting with abutment member 111 which, in turn, causes acorresponding change in the slope of the governor break, as desired.Reference is made to U.S. patent application Serial No. 92,876, filedMarch 2, 1961, in the name of Howard L. McCombs, Jr. (common assignee)for further details of operation of cam portions 93 and 99 andassociated linkage mechanism.

Operation of afterburner fuel control and exhaust nozzle control It willbe understood that, prior to initiating afterburner operation, certainvalves and associated structure of the afterburner fuel control 55 andexhaust nozzle control will occupy positions different from that shownin the drawings. For instance, referring to FIGURE 6, duringnonafterburning operation the fiapper will be held against orifice 670by the cam 673, such that valve 484 occupies a position to the leftagainst end portion 661 with lands 674 and 675 blocking passages 228 and652, respectively. The ratchet member 548 will be held in a downposition through levers 542 and 547 by the cam 545 whereby the ratchet589 is out of engagement with and below the end portion 50S of lever587. Likewise, the servo valve 555 and piston 557, as well as valve 563-attached to the latter, are at a down position whereby passage 567 invalve 563 is positioned below the adjacent end of passage 571 and valve563 rblocks passage 566 as well as passages 569, 570 and 571. Valve 622attached to valve 563 is positioned accordingly, such that land 624 isbelow the adjacent end of passage 449 and the three passages 449, 625and 626 are vented to passage 627. Valve 370 is urged to an openposition by the fuel from pump 77 and fuel flows through passages 360and 371 to valve 372 which is actuated to an open position therebypermitting fuel to fiow to passage 373 from which fuel fiows throughrestriction 366 and pressure regulating valve 333 to passages 331 and336. The fuel shutoff valves 338, only one of which is shown, arepressurized to a closed position Iby the fuel iiowing through associatedrestricted passage-s 447 and 448 and passages 449, 625 and 626. Thevalve 349 occupies a closed position whereby passage 348 is blockedpreventing fuel at regulated pressure Pr from reaching passage 350 whichresults in valve 345 being closed. The valve 349 is held in a closedposition by regulated pressure P1. which is admitted to chamber 352 inresponse to flapper valve 357 being biased against orifice 359 by lever360 which is loaded counterclockwise by spring 363.

Now, assuming that the throttle lever 54 is actuated to the positionrequesting full afterburner operation, the following sequence willoccur. The cam 673 will rotate in response to movement of the throttlelever 54 causing apper 671 to move away from orifice 670 into engagementwith orifice 669 as shown in FIGURE 6 whereupon vvalve 484 ispressurized to the right by the fuel pressure Pr acting against thetotal left hand end area of valve 484 in opposition to the force ofspring 677 plus fuel pressure Plr acting against the relatively smallarea of valve 484 exposed to end portion 662 plus the pressure Po actingagainst the remaining right hand end area of valve 484. Lands 674 and675 are displaced away from passages 228 and 652, respectively, therebyestablishing communication between passages 228 and 483 and betweenpassages 654 and 652. However, referring to FIG- URE 2, fuel atregulated pressure Pr is not permitted to flow to passage 483 until apredetermined high pressure compressor speed N2 is reached at which timethe arm 232 carried by piston 105 engages lever 230 causing valve 227 tomove upward, thereby communicating passage 226 with passage 228. Theresulting dow through passage 228 and 483 permits pressurization of thevarious servo lines in afterburner fuel control 55 and exhaust nozzlecontrol 70 which receive fuel at pressure P). from passage 483.

Referring to FIGURE 5, the cam 545, like cam 673, rotates with shaft 546as a function of throttle lever 54 position. Valve 543 follows adepressed contour of cam 545 allowing lever 542 and attached lever 547to pivot clockwise until the upper flat of ratchet 589 engages endportion 588 of lever 587 whereupon levers 542 and 547 are heldstationary. Fuel at pressure P1. flows through passages 560 and 559 tothe bottom side of piston 557 thereby urging piston 557 and attachedvalve 563 upward to a position whereby passage 567 communicates withpassage 571. As the piston 557 moves upward away from valve 555, theflow out of passage 556 increases causing a drop in fuel pressure at thebottom side of piston 557 and subsequent stabilization of piston 557.The valve 622 is actuated upward by valve 563 to a position whereby land624 vents passage 449 to drain fuel pressure PD. Venting passage 449 todrain fuel pressure P results in a drop in pressure in chamber 445whereupon shut-off valve 338 (FIGURE 4) opens in response to meteredfuel pressure P3 in conduit 336 thereby allowing fuel to ow to conduit56 which, in turn, supplies afterburner fuel manifold 38. Theafterburner fuel ow is ignited by conventional ignition means, notshown.

Referring to FIGURE 5, the lever 471 is pivoted counterclockwise aboutits connection with follower 473 in response to upward movement of lever472 which follows the aforementioned upward movement of valve 563causing valve 470 to move toward passage 462, thereby causing anincrease in fuel pressure at the bottom side of piston 461. The piston461 actuates spool valve 454 upward from the null position shown inFIGURE 5 thereby communicating passage 457 with passage 453 at high fuelpressure and passage 458 with passage 459 at drain fuel pressure whichresults in downward movement of piston 65 and opening movement ofexhaust nozzle gates 27.

As the exhaust gates 27 are controlled in an opening direction, fuelflow to the afterburner fuel manifold 38 is controlled through piston604 which rotates shaft 403 Carrying cams 402, 451 and 452 (FIGURE 4a).The lever 472, in its upward movement, actuates lever 615counterclockwise about its connection 612. The stop 616 on lever 615engages lever 611 urging the same counterclockwise about connection 612against the resistance of spring 613. The valve 609 moves accordinglytoward extension 608 causing a rise in servo fuel pressure againstpiston 604 which moves downwardly until stabilized by the follow-upaction of extension 608 which moves away from valve 609 thereby reducingthe servo fuel pressure acting against piston 604. The stops 616 and 617establish limits on the position of piston 604 as a function of theposition of throttle lever 54 between which limits the position ofpiston 604 is controlled as a function of the position of carn 474through follower 610.

The position change of exhaust nozzle gates 27 results in feedbackmovement of flexible link which rotates shaft 475 and fuel flow andnozzle correlation cam 474 secured thereto. The cam 474 actuatesfollower 473 causing lever 471 to pivot clockwise about its connectionwith lever 472, thereby moving valve 470 away from passage 462 which, inturn, results in a drop in fuel pressure at the bottom side of piston461 and corresponding downward movement of spool valve 454 to its nullposition whereby the exhaust nozzle gates 27 are stabilized. Thefollower 610 is positioned by its corresponding portion of cam 474 andmoves upward allowing lever 611 to pivot about connection 612 and underthe influence of spring 613, engage follower 610 whereupon furthermovement of follower 610 results in pivotal movement of lever 611 aboutconnection 612 between stops 616 and 617 which, in turn, positions valve609 thereby causing downward movement of piston 604 and a correspondingrotation of cams 402, 451 and 452.

The cam portion 101 (FIGURE 2) schedules turbine pressure ratio as afunction of speed N2 and inlet ternperature Ti by actuating roller 517to cause an increase or decrease in the effective lever arm of lever 514through which the spring 519 acts, thereby upsetting valve 513 in aclosing or opening direction depending upon the direction of movement oflever 514. The Valve 513 controls the fuel pressure acting againstpiston 506 which moves accordingly to rotate cam 482 which, in turn,positions roller 495. The position of roller 495 determines the pressureratio PT4/PT7 required to null the lever 489 and servo valve 488 securedthereto. The roller 530 attached to piston 506 provides a positionfeedback signal which results in a corresponding variation of theeffective lever arm of lever 52.8 to cause a position change of valve526 which, in turn, modifies the fuel pressure Ps in bellows 515accordingly to null the lever 514 loaded by bellows 515 in opposition tothe spring S19 and thus null the valve 513 whi-ch, in turn, results instabilization of piston 506.

If the area and fuel flow est-ablished by the aforementioned openingmovement of exhaust nozzle gates 27 tand downward movement of piston604, respectively, as a function of the position of throttle lever 54does not establish the pressure ratio PT4/PT7 required to null the lever489 and servo valve 488, the lpressure ratio sensing circuit whichincludes bellows 492 and 499 and associated linkage actuates the servovalve 488 toward an open or closed position depending upon the relativeerror in the pressure ratio PT4/PT7. For instance, assuming the pressurePT, downstream of turbine 30 to be in excess of that required toestablish the required pressure ratio PT4/PT7, the lever 489 will beunbalanced in a counterclockwise direction thereby actuating valve 488toward a closed position which, in turn, causes an increase in fuelpressure acting against piston 479 and movement toward the right, asviewed in FIGURE 5 of the same. The lever 477 is actuated-counterclockwise about its connection with piston 633 by the piston 479which results in rightward axial movement of cam 474 and subsequentmovement of followers 473 and 610 to cause a modification of the area ofexhaust nozzle gates 27 and fuel flow, respectively, which have theeffect of decreasing pressure PT-l thereby correcting the pressure ratioerror. The spool valve 454 is nulled in response to feedback movement ofexible link 75 which results in rotation of cam 474. The piston 479 andpiston 633 attached thereto via lever 477 provides proportional plusintegral oper-ation by means of which the cam 482 is actuated axially toactuate follower 502 and roller 495 attached thereto to a position whichsatisfies the null requirements of valve 488. The piston 479 providesproportional actuation `and the piston 633 provides integratingactuation. Only one axial position of the cam 482 will effect nulling ofthe valve 481 which controls pressurization of integrator piston 633which nulling must always occur therefor at the point corresponding tothe selected pressure ratio 'Pm/PTT The radial contour of cam 482 isconstant, such that rotation of cam 482 does affect the position offollower 631. The velocity of the piston 633 is controlled in Iaconventional manner by controlling the ow of servo `fuel thereto -aswill `be readily understood by those persons skilled .in the art.

Due to the time delay inherent in hydromechanical control mechanisms ofthe type under discussion whereby instantaneous control is not normallyavailable, it is desired to initiate an increase in exhaust nozzle areaslightly in advance of ignition of the afterburner fuel fiow to therebylead the resulting increase in pressure PT? downstream from turbine andhold the pressure ratio PT4/PT7 relatively stable. To this end, thecontour of cam 545 is `such that, with ratchet 589 engaged with endportion 588 of lever 587 as mentioned heretofore, the valve 543 ispermitted to move away from passage 541 thereby venting the same todrain pressure Po which, in turn, causes a drop in fuel pressure withinbellows 538. The bellows 538 contracts thereby allowing lever 528 tocontact the end of lever 528 which results in the force of spring 534acting against lever 528 thereby augmenting the force of spring 529which lever, in turn, is unbalanced in a counterclockwise direction. Theresulting increase in load against bellows 523 results in acorresponding decrease in ow through tubular member 527 which, in turn,causes an increase in pressure in passage S24 leading to the interior ofbellows 515 (FIGURE 2). The bellows S15 expands in response to theincrease in pressure therein and unbalances lever 514 in acounterclockwise direction thereby decreasing the flow area of valve 513which causes -a corresponding increase in pressure against the upperside of piston 506 which moves downw-ard as viewed in FIGURE 6 causingrack 505 to rotate shaft 503 and cam 482 attached thereto. The roller530 moves with rack 505 and decreases theeffective lever arm of lever528 through which the spring 529 acts thereby balancing the opposingtorques derived from lbellows 523 and spring 534 which results instabilization of lever 154 and attached valve 513 which, in turn,stabilizes the fuel pressure acting against piston 506 therebystabilizing the same.

The cam 482 rotates in response to movement of piston 506 yand urgesfollower 502 upwardly causing an increase in the effective lever arm oflever 489 through which bellows 499 acts and subsequent counterclockwisemotion of lever 489 which results in closing movement of valve 488 and acorresponding rise in fuel pressure against the one side ofproportionally acting piston 479. The proportionally `acting piston 479moves to the right causing lever 477 to pivot clockwise about itsconnection with piston 633 and actuate shaft 475 and cam 474 attachedthereto to the right. Also, the piston 479 actuates cam 482 to the rightcausing follower 502 to move downward in response to a depressed contourof cam 482.

The piston 604 is urged downward by the increase in `fuel pressure atthe top side thereof. Rack 412 att-ached to piston 604 rotates pinion413 causing shaft 403 and cams 402, 451 and 452 to rotatecorrespondingly. It will be understood that fuel is being supplied toafterburner manifold 38 only at this time since shut-off valves 338associated with a-fterburner fuel manifolds 39 and 40 are closed. Thecams 402, 451 and 452 are rotated clockwise looking from the driven endof shaft 403 and are provided Cil with a rising radial contour. Cam 402`rotates driving follower 401 upward which causes cam member 399 topivot counterclockwise thereby lifting follower 394 which, in turn,pivots lever 390 causing valve 386 to move away from passage 387 invalve 334 which results in a drop in fuel pressure PX in chamber 381 andsubsequent movement of valve 334 in yan opening direction. As valve 334moves in an opening direction, passage 387 moves toward valve 386thereby causing an increase in pressure PX in chamber 381 and subsequentstabilization of valve 334. The bel-lows 438 responds to the drop infuel pressure differential across valve 334 caused by opening movementthereof and actuates valve 437 away from passage 436 causing a drop 'infuel pressure PX at the face 430 of piston 429 thereby actuating valve335 in an opening direction to re-establish the predetermined constantpressure differential across valve 334 at which time the valve 33S isstabilized,

The shaft 403 and thus cams 402, 451 and 452 are positioned axially as afunction of the inlet temperature sensed by probe 61 which axialmovement of cam 402 results in corresponding movement of valve 386 andvalve 334 controlled thereby in the abovementioned manner. The positionof valve 386 land thus metering valve 334 is modified `as a function ofcompressor inlet pressure P1 which, in an increasing pressure sense,causes bellows 420 to expand thereby opening valve 418 and decreasingthe fuel pressure Ps acting on piston 417 which moves to the rightcausing counterclockwise movement of lever 414 until the lever 419 andvalve 418 attached thereto is stabilized by the follow-up motion ofroller 422 attached to piston 417. The movement of lever 414 results intranslatory motion of follower 394 which rotates on shaft 373 inresponse to the arm 398 following the inclined surface of ramp 399. Therotation of 4follower 394 results in actuation of lever 390 andcorresponding movement of valve 386 and metering valve 334.

Referring lback to FIGURE 5 and piston 479 which moves to the right inthe aforementioned manner, it will be noted that bracket 580 which moveswith piston 479 is adapted to engage screw member 579 thereby pivotinglever 573 clockwise causing v-alve 577 to move away from passage 576thereby venting the one side of piston 573 to drain fuel pressure P0whereupon the piston 573 is pressurized to the right against spring 574by fuel at regulated pressure PJr acting on the opposite side of piston573. Movement of piston 573 results in valve S82 integral therewithcommunicating passage 583 at regulated pressure Pr with passage 584leading to piston 585 which is pressurized against the spring bearingthereagainst causing stem 586 to engage lever 587 which, lin turn, ispivoted counterclockwise causing end portion 588 to release ratchet 589which permits levers 547 and 542 to pivot clockwise. The valve 555attached to lever 547 moves toward passage 556 causing an increase inpressure at the bottom side of piston 557 whereupon piston 557 movesupward displacing valve 563 accordingly. The passage 567 in valve 563moves out of engagement with passage 571 causing the fuel pressure ofthe left hand side of piston 573 to drop by virtue of the bleed passage576 which vents passage 572 to drain fuel pressure Po. The piston 573 isbiased -to the left by spring 574 whereupon valve 582 disestablishescommunication between passages 5183 and 584 and vents passage S84 todrain fuel pressure P0. The resulting drop in fuel pressure againstpiston 585 permits retraction of stem S06, allowing lever 587 to pivotclockwise causing end portion 588 thereof to engage the upper fiat ofratchet 590 as shown in FIGURE 5 which fixes the position lof lever 547and valve SSS attached thereto. The piston 557 and valve 563 attachedthereto assume a position in accordance with the fixed position of valve555 such that passage 567 communicates with passage 570 thereby ventingfuel at regulated pressure PT to passage 575 leading to piston 573.

The valve 622 follows the movement of valve 563 and

1. FUEL FLOW CONTROIL APPARATUS FOR A GAS TURBINE ENGINE PROVIDED WITHAN AFTERBURNER, A VARIABLE AREA EXHAUST NOZZLE AND A CONTROL LEVER FORCONTROLLING THE OPERATION OF THE ENGINE, SAID FUEL CONTROL APPARATUSCOMPRISING: A SOURCE OF PRESSURIZED FUEL; A CONDUIT CONNECTED TO DELIVERFUEL FROM SAID SOURCE TO THE AFTERBURNER; VALVE MEANS IN SAID CONDUITFOR CONTROLLING FUEL FLOW THERETHROUGH TO THE AFTERBURNER; FIRST MEANSOPERATIVLEY CONNECTED TO THE EXHAUST NOZZLE AND THE CONTROL LEVER FORVARYING THE AREA OF THE EXHAUST NOZZLE IN RESPONSE TO THE POSITION OFTHE CONTROL LEVER; SECOND MEANS OPERATIVELY CONNECTED TO SAID VALVEMEANS AND THE CONTROL LEVER FOR ACUATNG SAID VALVE MEANS IN RESPONSE TOTHE POSITION OF THE CONTROL LEVER; THIRD MEANS INCLUDING A ROTATABLY ANDAXIALLY MOVABLE NOZZLE AREA FEEDBACK CAM OPERATIVELY CONNECTED TO THEEXHAUST NOZZLE AND TO SAID FIRST AND SECOND MEANS FOR ACTUATING SAIDFIRST AND SECOND MEANS AS A FUNCTION OF THE EXISTING AREA OF SAIDEXHAUST NOZZLE; AND FOURTH MEANS RESPONSIVE TO THE PRESSURE RATIO ACROSSTHE GAS TURBINE OPERATIVELY CONNECTED TO SAID CAM MEANS FOR ACTUATINGTHE SAME; SAID CAM MEANS BEING OPERATIVE TO ACTUATE SAID FIRST ANDSECOND MEANS SIMULTANEOUSLY TO EFFECT A COORDINATED MODIFICATIN OFEXHAUST NOZZLE AREA AND AFTERBURNER FUEL FLOW.